Method of making safety paper



March 3, 1936. Q W, SMITH 032,816V

METHOD OF MAKING SAFETY PAPER Y l Filed Aug. 25, 1932 INVENTOR y BURGESS W. SMITH ATTORNEY Patented Mar. 3, 193@ UNTE@ ST Burgess W. Smith, Beachester,lila

Ene, Rochester, hh E21, a

'llhe Todd Company,

lil., msignor to corporation New Fiori-i Angust 35,

rei. simenon' invention relates to methods oi making' safety paper for paper forms, instruments, and other documents requiring protection against fraudulent alteration, and, more particularly, to the variety or safety paper embodying means adapted to be rendered operative on the applicaA tion or" chemical eradicators, to Warn oi attempted alteration. One object or" the invention is to provide a more simple and economical method of manufacturing such paper,

Another object is the provision of such a method capable of producing paper of white or uniformly tinted color, or having any desired pattern on it.

Another object is to provide a simple and inexpensive method of the character described, adapted for making paper containing an inherently warning word or other symbol, of an initially illegible character, but applied in a material which is reactive to chemical eradicating substances so as to develop a conspicuous color or stain upon the use of such substances in attempting alteration.

A further object is the provision of a method ci the character described in which the Warning symbol is appliedI to the lpaper in an initially illegible form but incorporated in the body of the paper itself, in a manner rendering it accessible to the eradicating substances, so as to secure conspicuous and permanent development oi the warning color or stairs,

To these and other ends the invention resides in certain method steps and combinations of steps, all as will be hereinafter more fully de scribed and pointed out in the claims at the end or the specication.

in the drawing:

Fig'. 1 illustrates, diagrammatically, one fom of equipment for practicing the invention; and

Fig. 2 illustrates in a general way one form or" safety paper which may be produced by the invention. f

It has been proposed heretofore to make safety paper by printing on it, before or after sizing, a pattern or symbol, with a colorless chemical or ink capable of reacting with chemical eradicators to develop a warning color or stain. It has been found, however, that the most eicient sensitive or developing chemicals for this purpose are generally of a more or less water soluble nature so that it has not been found practicable to apply such chemicals to thepaper during the formation of the same or prior to sizing because of the tendency of such chemicals to bedissolved and removed from the paper. It has been found, on the other hand, that the application o1 such Warning symbols to the paper after sizing, by the usual methods of printing, produces such a disturbance or" the surface of the paper that such symbols are initially legible because of the differ-s ence in the light reflecting action'of the papersurface, as between the printed and imprinted portions, particularly in certain angles or? incidence of the light, with the result that such initial legibility of the warning symbols renders the paper unsuitable for use.

My prior Letters Patent, Nos. fet'l, 1,675,769, and 1,689,392, describe and claim. methods of making safety paper which the initial illegibility of the Warning characters is insured by the use of a camoulaging pattern. My Letters Patent, No. 1,817,171, discloses and claims a further method of making such paper to reduce the legibility of the warning characters Where no camou'laging pattern is employed.

My present invention provides a further simple and inexpensive method for producing such paper, having various other advantages such as increased initial illegibility of the warning sym bols, the penetration of the sensitive chemical or ink into the paper to resist removal by abrasive methods, as well as accessibility to the action of eradicating chemicals to insure rapid and thorough development or the warning color or stain, as well as being generally available for making safety paper of various kinds and styles. In accordance with the' present invention it has been found that these advantages may be accomplished by printing the warning symbols on the paper after the sizing bath, while the paper is still moist or by moistening the formed paper before printinguv It has been found that by so printing on the moist paper with a chemical or ink that is miscible with water, or which conl tains dispersed therein active material soluble in water, it is possible to use a minimum of pressure, so as not to indent the paper, A's more fully described below'a suitable sensitive chemical or ink is employed of a substantially colorless nature, after the application of which the paper is driedA and finished, with the result that the chemical penetrates the paper and its presence is further obscured by the nishing operations,' so that it becomes completely invisible.

One variety of equipment or apparatus by which the invention may be produced is illustrated schematically in Fig. 1 of the drawing in which IU represents a supply roll of the paper web l2 passing under a roll i3, immersed in water or its equivalent in a vat 25, from which the web iscarried through squeeze rolls I4 and I5 to remove the surplus liquid. 'I'he web may then be passed directly to the printing rolls, hereafter described, but is preferably immersed a second time in the vat 25 under a roll I3 from which it proceeds through a second pair of squeeze rolls I1 and I8 which remove all but a trace of the liquid from its surface.

' receive a supply from the roll 22 supplied from the fountain 24 by means of an oscillating roll 23. This inking mechanism may have the usual or any suitable arrangement in accordance with the known construction commonly employed in printing presses.

In the vat 25 through which the paper passes kas described on the way to the printing device,

vI have used water without the admixture of any substances, or a siz`e adapted for the purpose, or I may use a colored bath of dye, or size containing the same, which will color the surface of the paper in a uniform tint where the rolls Il and I5, or I1 and Il, in case the latter are used, have plain or smooth surfaces. Should either pair of squeeze rolls be engraved with a pattern or design, such pattern or design will be impressed upon the paper in the manner described in Letters Patent to LaMonte and Saxe, No. 123,782. Such steps provide an economical and continuous method of marking the paper with a plain tint or color design or pattern, respectively, after which the paper so marked may be passed to the printing devices to there receive an .invisible printing of the warning symbols in a suitable chemical or ink applied to the roll Il by means of the mechanism described above.

A suitable, substantially colorless sensitive chemical or ink for applying the warning symbols by means of the roll Il is fully described in my copending application Serial No. 512,196, filed January 29, 1931, namely, a materialcomprising dlphenol and diphenyl-guanidine or related substances as described in said co-pending application. Conditions may make it desirable to use glycerine or similar hydroscopic material to prevent the chemical or ink from drying on the inking and printing rolls, as well understood in the art. I may also use such compounds as 1,3,5, aminomethvlchlorobenzothiazole, which may be in the form of the base, sulphate, hydrochloride or other salt dissolved or dispersed in a watermiscible medium, such as a solution of gum arabic in glycerine. It may also be ground into a varnish comprised of sulphonated oil, such as Turkey red oil. Such inks are substantially colorless and stable until reaction with a chemical eradicator with which they develop a conspicuous color or'stain ofl a permanent nature dimcult to remove. Y

From the printing rolls I9, 20, the paper web is preferably passed through drying rolls 26 and thence to a calender stack 21 and subsequently rewound in-a roll 2l. Instead of the calendering with rolls 21 some other form of nishing may be employed for removing any disturbance caused by printing of the homogeneous condition of -the paper surface.

While it is practicable to print, dry, and iinish the paper containing the warning symbols in a continuous operation as described, there are cerwarning symbol thus printed to be so diffused into the body of the paper that the outline of the letters of the warning word or symbol are blurred, instead of being sharp, which further reduces any tendency to initial legibility of the printing due to any slight color the ink may have. The described method further makes it possible to use 'a minimum of foreign matter in the preparation of the ink so that the active material is more easily acted upon by the chemical eradicator, thus increasing the rapidity and depth of color development. It will be seen that the above method is far more economicalI than the application of the sensitive chemical or ink to the paper by-addition, for example, to the beater or to a bath in which the paper is submerged, since the sensitive chemical or ink is generally of a more or less expensive character, especially in a pure state and good quality and since, by the present method, it is substantially all applied directly to the paper at those portions only desired to be treated with it. The final calendering or other finishing operation removes any disturbance of' the surface condition of the paper4 and affords a uniform and homogeneous appearance which completes the application of the warning symbols in a completely illegible manner.

The contents of vat 25 may include a coloring substance which is fugitive under the action of chemical eradicators or itself develops a warning color or stain in reaction therewith, as well understood in the art, and by providing one of the rolls I4, I5, or I1, Il with a desired design or pattern, the method may be advantageously employed to produce, instead of a uniformly white or tinted paper, a paper combining with the warning symbols a surface pattern adapted to protect against mechanical erasure orto ornament the paper.

.By the terms colorlessv or substantially colorless I mean that the warning words on the paper when finished will not be readable, and if the strength of the printing is sumcient to be readily readable when activated by an ink eradicator, the intention of the terms is correct.

I claim: l

1. The method of producing safety Paper comprising wetting said paper with a solution of a dye, pressing said paper between a pair of rolls one of which has its surface formed with a pattern to mark the paper and remove the surplus solution, printing from aV separately inked surfaceawarningsymbolonthcsurfaceofsaidwet paper with a water-miscible ink other than said Ihre, which ink is initially illegible and contains a substantially colorless compound 'adapted to be darkened by the action of an ink emdicator, and dryingandnnishingthepapersurfacesothat said warning symbol is not readable.

2. The method of producing safety paper oomprising wetting said paper with a solution of a' dye, pressing said paper between a pair of rolls oneofwhichhasitssurfaceformedwithapttem to mark the paper and remove the surplus solution, printing from a separately inked surface a warning symbol on the surface of said paper while moist land substantially without pressure with a water-miscible, initially illegible ink other than said dye containing a substantially colorless compound adapted to be darkened by the action of an ink eradicator, allowing said paper to stand for a substantial period to absorb said ink, drying said aper, and finishing its surface so that said vning symbol is not readable.

-3. The method of producing safety paper comprising moistening the paper with Water or a water solution, printing a warning symbol on the moistened paper with a printing surface separately inked with a water-miscible ink other than the substance with which said paper is moistened, which ink is initially illegible and contains a compound adapted to be discolored by the' action of the chemical eradicator, and drying and nishing the paper, so that said warning symbol is not readable.

4. The method of producing safety paper comprising moistening said'paper with water or a water solution, printing a warning symbol on said moistened paper without substantial pressure by means of a printing surface separately inked with a water-miscible ink other than the substance with which said paper is moistened, which ink is initially illegible and contains a compound adapted to be dscolored by the action oi.' ink eradicators, allowing said paper to stand for a. supstantial period to absorb said compound, and then drying the paper and finishing its surface,

so that said warning symbol is not readable.

5. 'Ihe method of producing safety paper comprising moistening said paper with a water solution of a dye, removing the surplus solution, printing a warning symbol on said moistened paper substantially without pressure by means of a printing surface separately inked with a Water-miscible ink other than said dye which ink is initially illegible and contains a substantially colorless compound adapted to be discolored by the action of an ink eradicator, drying said paper, and iinishing the paper surface, so that said Warning symbol is not readable.

BURGESS W. SMITH. 

